


Bound

by arcadenemesis



Series: As Prophecised [2]
Category: Voltron: Legendary Defender
Genre: Aftercare, Anal Sex, And Using Horns for Leverage, Because Demons like to cuddle too, Body Worship, Demon Sex, Demon Shiro (Voltron), Demon cock, Edging, Fingering, Fun with Forked Tongues, Keith (Voltron) is a budding Size Queen, M/M, Oral Sex, Orgasm Delay, Size Difference, Urban Fantasy, Warlock Keith (Voltron), belly bulge
Language: English
Status: Completed
Published: 2020-09-28
Updated: 2020-09-28
Packaged: 2021-03-08 01:26:54
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,965
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26697463
Author URL: https://archiveofourown.org/users/arcadenemesis/pseuds/arcadenemesis
Summary: Keith hums, letting silence fall between them for a moment as he stares the demon down as best he can from underneath him. Shiro doesn't budge, and it feels like a challenge."What if I gave you an order right now?""I would be obliged to carry it out," Shiro answers calmly.After the battle that brought them together, Keith tests the boundaries of the pact between him and his demon.
Relationships: Keith/Shiro (Voltron)
Series: As Prophecised [2]
Series URL: https://archiveofourown.org/series/1941031
Comments: 14
Kudos: 192
Collections: Bad Boys





	Bound

**Author's Note:**

> This AU is inspired by [St00pz](https://twitter.com/St00pzdraws) and is set just a short way into the journey Shiro and Keith embark on following Strings of Fate (first fic in the series).
> 
> It can be read as a standalone or as a continuation for greater context.

It's hard not to be captivated by Shiro. 

Traditional dynamics of their relationship—their _contract_ —dictate that he should be master and the demon his famulus, but then again, their bond isn't exactly...traditional. Keith still bears the mark on his cheek, the proof of the sacrifice Shiro made, willingly giving up his freedom to save Keith's life after the song of battle fell silent. He reaches up to touch it. The puckered flesh is a reminder of the lengths Shiro will go for him, and if he closes his eyes, Keith can still feel the sear of magic in his lungs, taste sweet lips pressed reverently to his.

It's something they've been dancing around; this lingering tension between them that crackles like static and sets Keith's nerves alight whenever Shiro responds to his summons. In the months since his father's disappearance, his demon has been a constant, faithfully by his side whenever Keith calls. Foes tremble before them both when the fight finds them, but Shiro is more than ferocious claws and dark magic. He's measured, thoughtful, gives Keith invaluable counsel—not at all how he envisioned a creature of the Underworld to be.

"I wasn't always this way," Shiro told him once, ruefully, when Keith had voiced that thought aloud. But when prodded for an explanation, Shiro had gone tight-lipped and rigid, and so Keith never asked him again. 

Perhaps he shouldn't be thinking of the demon with his violin in reach, certainly not when he takes to plucking the strings absently in his late-night musings. Keith shivers when smoke curls around him and hot breath ghosts over his ear.

"You rang?"

The smoke gathers in a swirl in front of him and the beautiful creature that occupies his mind solidifies in his room—all bar that strange, ghostly right arm. He copies Keith's posture, lips curled in amusement as his hulking frame comes to rest cross-legged on the other end of the bed. Keith snorts. It's ridiculous; knees dangling either side of the lumpy single mattress, he barely fits into the space. Shiro seems to notice too, glancing down, before running a critical eye over the derelict room, wrinkling his nose. 

"What are you doing in a place like this, angel?" 

Keith flushes. _Angel_ is a recent title, acquired somewhere between a bar fight with a bard in an Olkari tavern and a street skirmish with some hobgoblin who called himself General Morvok. It's nothing more than a joke to Shiro, so Keith valiantly fights down the heat in his gut that responds traitorously.

"I'm still working on that whole money thing," Keith grumbles, setting his violin down on the ground away from his wandering fingers. "A hostel room isn't free, and it turns out busking isn't the most lucrative occupation. Even with a magical fucking violin of terrible power, or whatever."

It's Shiro's turn to snort, leaning forward on his elbows. "Ah, then I'm here to Robin Hood you into the Four Seasons?"

Keith rolls his eyes reaching behind him to smack Shiro with the pillow he grabs. The demon simply bats it away with a laugh, grabbing Keith's arm and pulling him close.

"Then why did you call me?"

There is a genuine curiosity in the question, but it comes out low and quiet in a way that makes Keith shiver. He mutters a response that he _knows_ the demon can hear, but Shiro only grins with an amused glint in his eye. 

"Come again?"

"I said, it was an _accident_ ," Keith huffs, cheeks burning as Shiro laughs.

"And here I was thinking that that little instrument of yours only acted on your desires," Shiro teases. "Could it be that you desired my presence, angel?"

It's too close to the mark. Keith scrambles to deflect as he feels his stomach tie itself in knots. "You are so lame," he tells Shiro, who blinks in surprise as Keith pulls back. "Angels and demons, really? Uninspired."

"You don't like my puns?"

"I don't like it when you make fun of me."

Shiro stills, a troubled look washing over his face. "You think I'm mocking you?"

The way he speaks so softly makes Keith squirm. "Well…why else would you say it?"

Shiro rises so suddenly that it's instinct for Keith to retreat until his back hits the wall at the head of the bed. It doesn't perturb Shiro, eyes concerned as he crowds over him. That ghostly hand brushes over Keith's cheek and Keith releases a stuttering breath.

"You are so precious to me," Shiro says—whispers, even—in earnest. "You give me purpose. You give me freedom."

Keith scoffs, if only to try to ignore the thumping of his heart. He knows it's useless; Shiro must be able to hear it trying to crack past his ribs. "Yeah, for the whole three minutes before I nearly died and you gave it all up to save me."

"Free in everything but formality, then," Shiro grins. 

Keith hums at that, letting silence fall between them for a moment as he stares the demon down as best he can from underneath him. Shiro doesn't budge, and it feels like a challenge.

"What if I gave you an order right now?"

"I would be obliged to carry it out," Shiro answers calmly.

"You're not obliged," Keith says quickly, softer, chest pounding harder. Shiro tilts his head, patient as always, and Keith bites his lip. Uncertainty is a thing sewn into his very fibre in matters of the heart, and when it concerns one eldritch being, hovering over him, saying sweet words, he's only far, _far_ more out of his depth. Still, he can't be imagining this thing between them. And if he is, he'd rather put it to rest now.

"Kiss me."

Shiro goes as still as death, and Keith's heart drops. Of course. What was he thinking? He looks away, the words to tell Shiro to leave burning in the back of his throat, but then a hand moves to his chin, urging his eyes back. Wide-eyed, he looks for any sign of disgust in the demon's eyes, but only finds kindness and…relief? Shiro leans in close, and Keith swallows hard and lets his eyes fall closed as breath ghosts across his lips. But Shiro shifts on the bed, and then lips seal over the pulse point on his neck. Keith gasps, eyes flying open as a hand rises to sink into long hair on instinct. Shiro, the asshole, has the audacity to _grin_ against his skin, making his heart rate climb. 

"What are you—"

"You didn't specify _where_ to kiss you," Shiro says, all faux innocence as he pulls back and flesh fingers worm their way under his shirt. 

"Coy doesn't suit you," Keith grumbles, but it lacks any feeling and Shiro doesn't drop the act.

"Oh? Then maybe you meant…"

Shiro—all ten foot of his hulking frame—wriggles down the tiny bed, making Keith scoff. Before he can tell him how ridiculous he looks though, Shiro bows to press another kiss to the sliver of skin above Keith's hip bone. Keith isn't proud of the strangled sound that comes out of him, nor the whimper that follows.

"Shiro..."

His demon surges up at that, finally meeting his lips in a tender kiss. It's brief though, and Shiro pulls back with an oddly shy look.

"Is this okay?"

Keith only reaches up to pull him back down, meeting him with heat. It clearly takes Shiro by surprise, but he's quick to catch on, fingers gently kneading at his hip. Keith's body feels pliant under his hands, and this time, warmth pools in his gut instead of his lungs as Shiro kisses him.

"Keith..." the demon growls against his lips, a soft reminder of the question posed.

"Yes, yes, more than okay. Can't you tell by the way I, ah—"

The petulant response stops short when Shiro pulls back to ghost a hand over the inseam of his jeans. The chuckle that follows is both infuriating and endearing. 

"It's polite to ask first," Shiro grins. "I'm a demon, not an incubus."

"Could've fooled me," Keith deadpans as he feels his belt buckle loosen. It earns him a pout that makes him laugh.

"Unfair when you're the one who seduced me."

"Me?!" Keith splutters. "On what planet? Aren't you the one literally unzipping my pants right now?"

"Aren't you the one who ordered me to kiss you?"

Keith thinks he might be on fire. And losing the argument. "Shut up," he grumbles, half sitting up to pull his shirt over his head. The tactic works. Shiro looks stunned when he resurfaces from tattered cotton, lips slightly parted. Who knew demons could blush?

"Do I need to play a song for you to help you figure it out?" Keith teases, nodding down to where clawed hands lay frozen on his waistband.

"You bewitch me without music already."

Keith searches for the mocking tone, mouth opening and closing soundlessly, but when he finds nothing, he hides his face under the shirt in his hands, flopping backwards onto the mattress again. 

"Too much?" he hears Shiro ask as fingers trail down his belly feather-light. He sounds entirely unapologetic.

"Just keep undressing me," he answers, muffled, before softly adding, "Please."

There's a rumble of acknowledgement above him, before Keith feels his top button pop open and denim peeled down his legs. He already knows he's embarrassingly hard, but a flush still goes through him when he feels his cock bob against his belly. A hand only lifts the shirt over Keith's face so far as to softly kiss his lips, but no relief comes in the form of touch.

"You look like a feast, angel."

Shiro's voice sounds so affected that Keith can't help but pull the shirt away so take a peek at him.

"Fuck."

Whatever illusion the demon uses to preserve his modesty is well and truly dissolved, greeting Keith with the sight of Shiro slowly stroking his own cock. It's reflex for Keith to gulp; thick, uncut and curved upward in a way Keith knows he would be able to feel inside him for days. Precome beads generously at the swollen tip, gathered on every lazy upstroke of Shiro's hand to spread down his already slick shaft. 

"Stay there," Shiro urges, placing a hand on Keith's chest when he attempts to sit up. "Let me serve you."

"This isn't—"

Keith's protest hitches in his throat when Shiro dips down to kiss at the juncture of his thigh and hip, chuckling quietly.

"I know, I know. But let me."

It's all Keith can do not to whine pitifully as Shiro pulls back, only to take him into his mouth without warning. The inhuman heat reminds him just who he is dealing with as Shiro sinks down and gently circles a slick finger at his entrance. The buzz that settles under his skin is like the opening notes to a song, and Keith stares at the ceiling as he lets it wash over him. Shiro takes his time, making the stretch barely noticeable as he presses a finger inside of him. For a moment, it's almost easy to forget how the demon dwarfs him…until Keith looks down to see his hulking figure between his legs, ghostly fingers gripping his thigh.

"Gods…"

Shiro hums, and Keith feels it like an earthquake through his body, shuddering a breath. Shiro pulls away, eyes locked on his as his tongue splits and laves either side of his cock. Keith almost comes from that sight alone. If the way Shiro grins is any indication, he must know.

"Since when have you had a fucking forked tongue?" Keith wheezes, because he thinks Shiro's touch might be making him dumb, but surely he would have noticed _that_ before. Shiro only laughs.

"You don't really get the whole shape-shifting thing, do you, baby?" he teases, pointedly clicking his tongue. Keith feels his face burn. Theoretically, yes, he knows changing form is well within the demon's power. How couldn't he know when the vision of a human face with grey eyes breathing life into him is branded into his memory? Still...

"Shut up," he answers again, heated. 

He sits up, ignoring the creak of the bed as he pushes Shiro back until he's sitting on the mattress again. He takes some satisfaction in Shiro's look of surprise as he straddles his hips, feeling the immediate burn of the stretch in his thighs to plant his knees either side of him. Keith reaches out to grip onto one of the horns curling from Shiro's crown to steady himself. There's a hand at his back to secure him, fingers stroking the column of his spine.

"Fuck me," Keith says, and it comes out like a plea instead of a demand this time. Shiro groans and Keith grinds back against the demon's cock as it jumps against his ass. Shiro answers him with a filthy kiss, but just as Keith starts to feel dizzy with breathless want, he feels himself shifting on his knees involuntarily. It doesn't take long for him to figure out what's going on, breaking the kiss with a frown.

"Just what do you think you're doing?" he asks, tugging on the horn on the left side of Shiro's head, as if that might stop him from shrinking his massive body down. It does make Shiro pause, and after a beat, large hands come to rest on his hips.

"...I don't want to hurt you," Shiro says cautiously. Keith barely hears him, brain short-circuiting at the sudden realisation that Shiro could encircle his waist with his bare hands. Shiro seems to notice too, if the way he swallows and his eyes flick down when his fingers flex against his skin is any indication. Keith tugs on his horn to bring his gaze back up to meet his again.

"Shiro," he says, giving him a flat look. "Have you forgotten who I am? What I can do? You won't hurt me."

To his credit, Shiro does look a little sheepish, but there's still an edge of uncertainty to his voice when he says, "Angel…"

Keith cocks an eyebrow in challenge. 

"Are you not here to serve me?"

There's a moment of silence, where Keith thinks maybe he's said the wrong thing, crossed some unspoken line... But then wicked mirth glints in grey eyes, sending a shiver up his spine.

"Whatever you command...master."

Shiro drops lips to Keith's shoulder as his hands slide to his ass, sucking a bruise into his skin while he gently kneads his flesh. It's a bright spark of pain as teeth join in too, making Keith gasp, and already it feels wonderfully animalistic as the slick head of Shiro's cock bumps against his entrance. A small voice of self-preservation tries to warn him; it feels impossibly large, maybe too much for his body to handle, but it's drowned out by the possessive rumble coming from Shiro's chest. 

"Hold on, angel," he tells him, and Keith grabs blindly, fingers gripping both horns. Shiro chuckles, and Keith feels it reverberate through him like his music. "Breathe."

It's excruciatingly gentle as Shiro presses inside of him bit-by-bit. The stretch comes quickly though, and Keith fights his body's urge to clamp down, fingers tightening on Shiro's horns as he inhales slow through his nose. Shiro takes it as a cue to pause though and Keith whines.

"Keith..."

"I'm not going to break."

Keith knows he sounds like a brat, but Shiro doesn't respond in kind. The hands on his hips run up his side, soothing. Keith drops his own hands down to Shiro's arms, squeezing in weak protest. Shiro curls forward to nose at the side of his neck, and Keith knows it's an attempt to comfort him, to give him a way out. It's almost a little tempting. Maybe this is too much. Shiro is impossibly huge, far more than any ordinary human could be expected to bear. And what if Shiro takes little joy from this struggle? Maybe he would prefer to seek his pleasure elsewhere?

"We have all night. We have other nights. There's no rush."

The thought of _other nights_ makes heat flood through Keith's veins, determination renewed. He knows his body has its limitations. Limits were meant to be exceeded, though. Perhaps one day he'll be able to do this without magic, but for now...

Keith relishes in Shiro's involuntary gasp as he feels his body begin to yield. It doesn't make the sensation any less consuming; Keith feels every inch of Shiro's girth as he bears down, feels every throb of both their bodies as his heart quickens and pounds. It takes time, but Shiro groans as Keith bottoms out, and Keith doesn't protest when Shiro holds him still. It feels like Shiro is pressing up against his lungs as he tries to catch his breath.

"Told you," he gasps, as Shiro's claws dig into his skin.

"Holy hell," Shiro whispers, voice choked as Keith recovers to grind into his lap. Keith laughs airily, cupping Shiro's face to bring their lips together in a graceless kiss. It takes a moment for Shiro to catch up, but Keith can't stop a sound of surprise when he feels a forked tongue flick against his. Shiro grins in the kiss, and so Keith retaliates by rocking against him as best as he can. Shiro tenses and groans, pulling back. "You're going to kill me, angel."

But it isn't enough for Keith. He knows he can do more. With one hand on Shiro's shoulder, he reaches to grip Shiro's horn with the other, hauling himself up until most of Shiro's cock slides out of him. The drag is brutal, unending, but Keith doesn't give either of them time to react before he slams down again, groaning in tandem with Shiro this time. The demon is everywhere, surrounding him, crowding him. Keith feels so full, so utterly overflowing with the sensation of just Shiro, Shiro, Shiro…

"Fuck, angel. Is that me?" Shiro breathes. 

Keith glances down when fingers brush over his belly, seeing the swell that has caught his demon's attention. A surge of pride burns unbidden in Keith's chest, but it's hardly a surprise to him when he feels every inch of demon cock inside of him. He covers Shiro's hand with his own, pressing it tight to his stomach as he pulls himself up and down again, slower this time, feeling the way his belly shifts against Shiro's palm as he fills him again.

"You feel so good," he half-slurs, body starting to hum. "Can feel you everywhere." The demon's eyes still haven't left their joined hands. There's a rumble in Shiro's chest, and Keith can tell it's taking all his self-control to hold still. 

"Come on, Shiro," Keith urges. Shiro's jaw only tightens, and suddenly Keith feels himself become desperate, words almost begging. "Please, Shiro. I need you. Please. I—"

With a growl, the world suddenly spins around Keith until the mattress rises to meet him at his back. Shiro is there in an instant, hoisting one of Keith's knees over a massive shoulder as best he can, bearing down on him. Even now though, he pauses.

"I'm yours," Shiro says reverently; a reaffirmation of his oath, but Keith senses something more in those words.

"And I'm yours," he whispers back, reaching up to kiss his bottom lip as grey eyes go wide. "So take me."

Finally that thread of control snaps, and Shiro's hands are everywhere as he thrusts forward and Keith sees supernovas burst before his eyes. Keith surrenders to the pace and the violent build of pleasure that chases it. The bed frame creaks dangerously beneath them in protest, but Keith can't find it in him to care if it splinters or breaks. All that matters right now is this moment of ever-mounting ecstasy, the escape from the mortal world around them, this feeling of belonging to someone. 

Shiro is all that matters.

When he had envisioned this moment, fantasised wildly of things he thought would never come to pass, Keith had imagined this raw strength, this brutal pace. He had come alone dozens of times to the thought of Shiro pinning him down and staking his claim. But he hadn't pictured it all; not the tender grip on his hip that would still bruise in the morning, not the tickle of long hair brushing at Keith's neck whenever whispered words of nonsense and praise come close. Certainly not the kisses stolen from the corners of his lips on shallower thrusts. It's better than his imagination, and Keith almost feels ashamed to have not realised Shiro would be as generous in this as he is in all other things. There's a wildness to the way Shiro fucks him, but the demon keeps shifting and searching to make Keith cry out over and over until his throat feels hoarse. If he were a little more lucid, he might spare thought for the hostel patrons on the other side of the paper-thin walls. Whether he would care is another thing entirely. 

Shiro brings him to the edge over and over until tears gather in the corners of his eyes, backing off to pet at his belly or brush the hair from his eyes or nip at his neck, never quite letting him plunge toward his end.

"Doing okay, angel?" he asks as he slows his pace for a fifth time, causing Keith to let out a frustrated whine. He nods, though, and Shiro rewards him with a kiss, burying himself deep and sending sparks of heat through his veins. 

"Last one," Shiro promises, left hand moving to cover Keith's where he grips the pillow above his head.

The final build-up is almost too much for his body to contain, and though Keith would gladly drown in Shiro forever, he can't help the sob of relief when the demon finally wraps ghostly fingers around his aching cock, nudging him over the edge into a release that feels violent and unearthly. Keith is still in the grips of his own pleasure when Shiro spills with a groan, molten hot inside him. He blinks away the spots in his vision, trying to take stock of his body as Shiro stills. There's a moment of quiet calm between them, where their mingled breath and the rush of blood in his ears is all that Keith hears, but slowly Shiro starts to move again. With limited success, Keith tries not to whimper as Shiro draws back, mourning the fullness and warmth as it leaves.

"It's okay, angel. I'll clean you up," Shiro says, bringing his attention to the sticky rush between his legs. Keith pouts.

"Not yet," he grumbles. "Stay here."

Shiro's chuckle sounds as tired as it does fond, and Keith takes some pride in the idea that he may have exhausted the demon.

"Oh angel," he sighs as he rolls onto his side, crammed up against the wall, "you can play me like a—"

"Don't say it. Don't you dare say—"

"—fiddle."

"Urgh." But Keith knows the uncontrollable curve of his lips undermines the groan. "You are insufferable."

Shiro grins down to him, stroking his cheek with a long finger. "Is that my dismissal?"

Keith answers by shoving Shiro' shoulder, nuzzling in close to rest his cheek on his chest as they lay on the tiny bed.

"You're free to go whenever you want," Keith says quietly, hiding his face, scared that he might look as vulnerable as he feels. But strong arms wrap around him, pulling him closer, and Keith feels himself melt into the hold.

"Sleep, angel," Shiro tells him, voice sweet and low. "I'll be here when you wake."

**Author's Note:**

> It's not often I write something in the realms of PWP but I did it for the Bad Boys Sheith Zine so please blame them.
> 
> You can find me on [Twitter](https://twitter.com/copilotsheith/status/1310594309737963521?s=19).


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